Liquid injection device

ABSTRACT

A liquid injection device includes: a chamber which supply of the liquid and connects with the injection nozzle; a chamber volume varying unit to which driving voltage is applied to reduce the volume of the chamber to a volume smaller than the volume of the chamber before the driving voltage is applied; a driving voltage applying unit which applies the driving voltage to the chamber volume varying unit with the liquid supplied to the chamber; a pseudo noise data memory unit which stores sound data of pseudo noise having audible frequency components contained in driving noise generated when the driving voltage is applied to the chamber volume varying unit; and a pseudo noise outputting unit which outputs the pseudo noise by using the sound data of the pseudo noise such that the sound pressure of the driving noise decreases within the audible frequency range when the driving voltage is applied.

This application claims priority to Japanese Patent Application No.2010-065849, filed on Mar. 23, 2010, the entirety of which is herebyincorporated by reference.

BACKGROUND

1. Technical Field

The present invention relates to a technology for injecting liquid froman injection nozzle.

2. Related Art

Recently, a method of incising or excising a living tissue by usingliquid such as water and a physiological salt water injected from aninjection nozzle toward the living tissue at a high pressure has beendeveloped as a surgical method. A liquid injection device employed forthis method includes a liquid chamber filled with liquid to be injectedfrom the injection nozzle, and an actuator for varying the volume of theliquid chamber (JP-A-2008-082202). According to this structure, thevolume of the liquid chamber decreases in accordance with operation(expansion) of the actuator. As a result, the liquid within the liquidchamber is pressurized and injected as high-pressure liquid from theinjection nozzle.

However, when bubbles are contained in the liquid chamber of the liquidinjection device thus constructed, these bubbles contract and absorb thepressure applied to the inside of the liquid chamber. In this case, theliquid within the liquid chamber receives only insufficientpressurization, and thus the capability of incising or excising theliving tissue lowers. Therefore, when bubbles are mixed or generated inthe liquid chamber, the operation needs to be temporarily stopped so asto remove the bubbles within the liquid chamber by discharge through theinjection nozzle or by other methods.

Under the normal operation condition of the liquid injection device(without mixture of bubbles into the liquid chamber or other abnormalconditions), driving noise (chiefly constituted by vibration noiseemitted from a component for fixing the actuator or other noise) isgenerated by the effect of the force produced at the time ofpressurization of the liquid within the liquid chamber in accordancewith the expansion of the actuator. On the other hand, when the abnormaloperation condition such as mixture of bubbles into the liquid chamberoccurs, the driving noise generated from the liquid injection devicetends to decrease (the frequency or amplitude of the driving noisechanges).

However, the tendency of the liquid injection device to decrease thedriving noise in accordance with the abnormal operation condition suchas mixture of bubbles is completely opposite to the general idea thatlarge abnormal noise generates when a device is in some abnormaloperation condition. Thus, an operator of the liquid injection devicecontinues using the device without noticing occurrence of theoperational abnormality (existence of bubbles within the liquid chamber)in some cases.

SUMMARY

An advantage of some aspects of the invention is to provide a technologycapable of solving the problems arising from the related art describedabove, as a technology allowing an operator to easily recognizeoccurrence of an abnormal operation condition such as mixture of bubblesinto a liquid chamber.

A liquid injection device injecting liquid from an injection nozzleaccording to an aspect of the invention includes: a liquid chamber whichreceives supply of the liquid and connects with the injection nozzle; aliquid chamber volume varying unit to which driving voltage is appliedto reduce the volume of the liquid chamber to a volume smaller than thevolume of the liquid chamber before the driving voltage is applied; adriving voltage applying unit which applies the driving voltage to theliquid chamber volume varying unit with the liquid supplied to theliquid chamber; a pseudo driving noise data memory unit which storessound data of pseudo driving noise having at least a part of audiblefrequency components contained in driving noise generated when thedriving voltage is applied to the liquid chamber volume varying unit;and a pseudo driving noise outputting unit which outputs the pseudodriving noise by using the sound data of the pseudo driving noise suchthat the sound pressure of the driving noise decreases within theaudible frequency range when the driving voltage is applied.

The liquid injection device according to this aspect of the inventionpressurizes the liquid within the liquid chamber and ejects thepressurized liquid from the injection nozzle as pulses by applyingdriving voltage to the liquid chamber volume varying unit under thecondition in which the liquid is supplied to the liquid chamber. In thiscase, driving noise is generated by effect of the reaction forceproduced by pressurization of the liquid within the liquid chamber whenthe driving voltage is applied. The liquid injection device of thisaspect of the invention stores sound data of pseudo driving noise havingat least a part of the audible frequency components contained in thedriving noise, and outputs the pseudo driving noise for reducing thesound pressure of the driving noise in the audible frequency range byusing the sound data of the pseudo driving noise when the drivingvoltage is applied. The phrase “reducing the sound pressure of thedriving noise in the audible frequency range” herein refers to acondition in which the driving noise is not required to be completelycancelled but may be only reduced to have a sound volume smaller for theears of an operator of the liquid injection device than that of thedriving noise when the pseudo driving noise is not outputted.

According to this structure, at least a part of the driving noisegenerated when the driving voltage is applied can be cancelled by thepseudo driving noise outputted when the driving voltage is applied underthe condition in which no bubble is contained in the liquid chamber. Asa result, the operator of the liquid driving device feels that thedriving noise has decreased to be smaller than the driving noisegenerated when the pseudo driving noise is not outputted. However, whenbubbles are mixed into the liquid chamber, these bubbles contract andchange the reaction force produced when the liquid within the liquidchamber is pressurized. As a result, the frequency and the soundpressure of the driving noise generated when the driving voltage isapplied are changed. In this case, the pseudo driving noise outputtedbased on the stored sound data does not cancel the changed drivingnoise, and thus the operator hears both the changed driving noise andthe pseudo driving noise. Accordingly, the pseudo driving noise whichcancels and reduces the driving noise when no bubble is contained in theliquid chamber becomes noise (alarm) when the driving noise is changedby mixture of bubbles into the liquid chamber. In this condition, theoperator feels that the noise coming from the liquid injection devicehas suddenly increased, and easily recognizes mixture of the bubblesinto the liquid chamber.

When the normal condition is restored by discharge of the bubbles mixedinto the liquid chamber from the injection nozzle or by other methods,the driving noise and the pseudo driving noise again come to becancelled by each other. As a result, the operator feels that the noisehas decreased, and easily recognizes discharge of bubbles from theinside of the liquid chamber. Since the relationship between thepresence or absence of bubbles within the liquid chamber and theincrease or decrease of the driving noise felt by the operator becomesan ordinary relationship in which noise increases when an abnormalcondition occurs, the operator can intuitively recognize the presence orabsence of bubbles. Thus, the liquid injection device can be constantlyused in an appropriate condition.

The liquid injection device of the above aspect of the invention maystore the sound data of the pseudo driving noise in accordance with thedriving voltage applied to the liquid chamber volume varying unit.

The liquid injection device can change the driving voltage applied tothe liquid chamber volume varying unit (such as the level of the applieddriving voltage, the waveform of the applied driving voltage, and theperiod of the applied driving voltage) so as to switch the mode ofliquid injection from the injection nozzle. The change of the drivingvoltage applied to the liquid chamber volume varying unit varies thefrequency and the sound pressure of the driving noise generated when thedriving voltage is applied. Thus, when sound data of the pseudo drivingnoise suited for reduction of the sound pressure of the driving noise(reduction of the noise) is stored in correspondence with the drivingvoltage applied to the liquid chamber volume varying unit, appropriatereduction of the driving noise can be achieved by using the pseudodriving noise outputted based on the sound data of the pseudo drivingnoise corresponding to the applied driving voltage. In this case, thepseudo driving noise heard as noise is felt as larger noise when bubblesare mixed into the liquid chamber. Thus, the operator can further easilyrecognize mixture of bubbles into the liquid chamber.

The liquid injection device of this aspect of the invention may decreasethe sound pressure of the driving noise within the audible frequencyrange by outputting the pseudo driving noise with delay from the timewhen the driving voltage is applied.

The driving noise is generated when the driving voltage is applied. Whenthe pseudo driving noise is outputted with delay from the time when thedriving voltage is applied, the phase of the pseudo driving noise can beshifted such that at least a part of the driving noise can be cancelledby the pseudo driving noise. As a result, the operator can easilyrecognize mixture of bubbles into the liquid chamber when bubbles aremixed into the liquid chamber.

The liquid injection device of this aspect of the invention may have anoutput timing control unit which controls the time when the pseuddriving noise is outputted with delay from the time when the drivingvoltage is applied.

When the output timing of the pseudo driving noise is controlled suchthat the driving noise practically generated can be reduced to theminimum, the appropriate output timing can be easily established.Moreover, the driving noise can be appropriately reduced.

The liquid injection device of this aspect of the invention maydecreases the sound pressure of the driving noise in the audiblefrequency range by outputting the pseudo driving noise having the phaseopposite to the phase of at least a part of the audible frequencycomponents of the driving noise in accordance with the time when thedriving voltage is applied.

As explained above, the driving noise is generated when the drivingvoltage is applied. When the pseudo driving noise having the phaseopposite to the phase of the driving noise is outputted in accordancewith the time when the driving voltage is applied, at least a part ofthe driving noise can be cancelled by the pseudo driving noise. As aresult, reduction of the driving noise can be achieved. In this case,the pseudo driving noise is only required to be outputted in accordancewith the time when the driving voltage is applied. Thus, control overthe output timing is facilitated.

The liquid injection device of this aspect of the invention may performthe following processes. Initially, the driving noise generated when thedriving voltage is applied is obtained by a driving noise obtainingunit. Subsequently, sound data of the pseudo driving noise is producedbased on the obtained driving noise, and then stored.

According to this structure, sound data of the pseudo driving noisesuited for reduction of the driving noise generated when the drivingvoltage is applied can be produced based on the practically generateddriving noise. In this case, the driving noise can be appropriatelycancelled by the pseudo driving noise outputted based on the sound dataof the pseudo driving noise for reduction of the driving noise.Accordingly, the operator can easily recognize mixture of bubbles intothe liquid chamber when bubbles are mixed into the liquid chamber.

The liquid injection device of this aspect of the invention may storesound data having the sine waveform corresponding to any one frequencyof audible frequency components contained in the driving noise as sounddata of the pseudo driving noise.

The driving noise practically generated when the driving voltage isapplied contains various frequency components. Thus, reduction of thedriving noise can be easily achieved by outputting the pseudo drivingnoise based on sound data having the sine waveform corresponding to anyone frequency of the audible frequency components contained in thedriving noise as the sound data of the pseudo driving noise.Particularly, when the pseudo driving noise is outputted based on thesound data having the sine waveform corresponding to the frequency ofthe components having the highest sound pressure in the driving noise, ahigh noise reduction effect can be produced.

The liquid injection device of this aspect of the invention may performthe following processes. Initially, a sine wave control unit whichcontrols at least either the phase of the sine waveform or the amplitudeof the sine waveform is provided. The pseudo driving noise is outputtedby using sound data of the pseudo driving noise obtained after controlof at least either the phase or the amplitude of the sine waveform.

When the phase or the amplitude of the sine waveform is controllable inaccordance with the actual driving noise as in this structure, thewaveform of the pseudo driving noise to be outputted can be made similarto the waveform of the driving noise. Thus, reduction of the drivingnoise can be achieved with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 illustrates the general structure of a liquid injection deviceaccording to an embodiment.

FIGS. 2A and 2B are cross-sectional views illustrating the structure ofan injection mechanism mounted on the liquid injection device accordingto the embodiment.

FIG. 3 illustrates through holes formed on a case of the injectionmechanism.

FIG. 4 is a flowchart showing the flow of a process performed by theliquid injection device according to the embodiment for outputtingcancel sound (cancel sound control process).

FIGS. 5A through 5D show a condition in which cancel sound functions asalarm when an abnormal operation condition such as mixture of bubblesinto a liquid chamber of the injection mechanism occurs.

FIG. 6 illustrates the structure of an injection mechanism mounted on aliquid injection device according to a first modified example.

FIG. 7 shows a concept of cancel sound data stored beforehand for eachof plural established driving voltage patterns with correlations betweenthe cancel sound data and the driving voltage patterns.

FIGS. 8A through 8D show a condition in which a liquid injection deviceaccording to a second modified example reduces driving noise by usingcancel sound outputted based on sine wave cancel sound data.

DESCRIPTION OF EXEMPLARY EMBODIMENT

An embodiment according to the invention is hereinafter described in thefollowing order for clarifying the details of the invention.

A. Device Structure:

A-1. Structure of Liquid Injection Device:

A-2. Structure of Injection Mechanism:

B. Cancel Sound Output Operation in This Embodiment:

C. Modified example:

C-1. First Modified Example:

C-2. Second Modified Example:

A. Device Structure A-1. Structure of Liquid Injection Device

FIG. 1 illustrates the general structure of a liquid injection device 10according to this embodiment. The liquid injection device 10 shown inthe figure is employed for performing an operation which incises orexcises a living tissue by injecting liquid such as water andphysiological salt water toward the living tissue at a high pressure.However, the liquid injection device 10 may be used for other purposes.

As illustrated in the figure, the liquid injection device 10 in thisembodiment includes an injection mechanism 50 for pressurizing liquidsuch as water and physiological salt water and injecting the pressurizedliquid, a supply pump 150 for supplying liquid to be injected toward theinjection mechanism 50, a liquid tank 160 for containing liquid to beinjected, and others. The supply pump 150 is connected with the liquidtank 160 via a liquid channel 152. Liquid sucked from the liquid tank160 by using the supply pump 150 is supplied to the injection mechanism50 via a connection tube 140.

A channel tube 130 having an injection port 132 (injection nozzle) atthe top end is connected with the injection mechanism 50 such thatliquid pressurized within the injection mechanism 50 can be conveyedthrough the channel tube 130 and injected from the injection port 132 atthe top end. For incising or excising a living tissue, an operator ofthe liquid injection device 10 holds a case 100 of the injectionmechanism 50 and ejects liquid while pointing the injection port 132 atthe living tissue as the incision or excision target.

A-2. Structure of Injection Mechanism

FIGS. 2A and 2B are cross-sectional views illustrating the structure ofthe injection mechanism 50 mounted on the liquid injection device 10according to this embodiment. As illustrated in FIG. 2A, the injectionmechanism 50 includes a liquid chamber 102 filled with liquid such aswater and physiological salt water, a supply channel 104 for guidingliquid supplied by the supply pump 150 toward the liquid chamber 102, aninjection channel 106 for guiding liquid within the liquid chamber 102toward the channel tube 130, and others, and all of these components areaccommodated within a case 100 made of lightweight material having acertain strength such as plastics. One end surface of the liquid chamber102 corresponds to a diaphragm 108 formed by a thin metal plate or thelike.

A piezoelectric device 110 as an actuator for varying the volume of theliquid chamber 102 is provided within the case 100 of the injectionmechanism 50. The piezoelectric device 110 is fixed to a plate-shapedmember 114 called a bottom plate. Under the condition in which thepiezoelectric device 110 is accommodated within a cylindrical housing112 to which the plate-shaped member 114 is fixed, the piezoelectricdevice 110 comes into contact with the surface of the diaphragm 108 onthe side opposite to the liquid chamber 102 such that the piezoelectricdevice 110 and the diaphragm 108 can be bonded to each other. Thepiezoelectric device 110 thus disposed expands when driving voltage isapplied thereto. This expansion of the piezoelectric device 110 allowsinjection of liquid in the following manner.

Initially, when driving voltage is not applied to the piezoelectricdevice 110, the piezoelectric device 110 does not expand as illustratedin FIG. 2A. In this condition, the liquid chamber 102 is filled withliquid such as water and physiological salt water supplied from thesupply pump 150. When driving voltage is applied to the piezoelectricdevice 110 from a not-shown power source (driving voltage applying unit)with the liquid chamber 102 filled with liquid, the piezoelectric device110 expands and pushes the diaphragm 108 toward the liquid chamber 102as illustrated in FIG. 2B. As a result, the volume of the liquid chamber102 decreases, thereby pressurizing the liquid within the liquid chamber102. As explained above, the two channels of the supply channel 104 andthe injection channel 106 are connected with the liquid chamber 102.However, since these channels 104 and 106 are narrow, the liquidcontained in the liquid chamber 102 can be sufficiently pressurized byreduction of the volume of the liquid chamber 102 in accordance with theexpansion of the piezoelectric device 110. Accordingly, thepiezoelectric device 110 and the diaphragm 108 constitute a liquidchamber volume varying unit for reducing the volume of the liquidchamber 102.

The pressurized liquid within the liquid chamber 102 is pushed outtoward the injection channel 106 connected with the liquid chamber 102.In this case, the liquid within the liquid chamber 102 is pushed notonly toward the injection channel 106 but also toward the supply channel104. However, since the easiness of introduction of liquid into achannel is determined by the length, the cross-sectional area and thelike of the channel, the flow amount of liquid into the supply channel104 can be made smaller than the flow amount of liquid into theinjection channel 106 by setting the lengths and the cross-sectionalareas of the supply channel 104 and the injection channel 106 in anappropriate manner. By this method, most of the pressurized liquidwithin the liquid chamber 102 is pushed toward the injection channel106, and then conveyed through the channel tube 130 and injected fromthe injection port 132 at the top end at a high flow speed. According tothe liquid injection device 10 in this embodiment, the inside diameterof the injection port 132 is made smaller than the inside diameter ofthe channel tube 130. Thus, the flow speed of the liquid injected fromthe injection port 132 can be further increased.

After the liquid is injected in the manner described above, the drivingvoltage applied to the piezoelectric device 110 is stopped (the drivingvoltage is reduced) to return the length of the piezoelectric device 110to the original length. As a result, the volume of the liquid chamber102 is returned to the original volume, allowing liquid to be suppliedfrom the supply pump 150 to the liquid chamber 102 (see FIG. 2A). Whenthe piezoelectric device 110 is again expanded by applying the drivingvoltage thereto (see FIG. 2B), liquid can be again injected from theinjection port 132 at a high flow speed. Accordingly, the liquidinjection device 10 in this embodiment achieves injection of liquidhaving a high flow speed as pulses by repeating these processes, andincreases the capability of incising or excising a living tissue byutilizing a high pressure produced when the liquid injected at the highflow speed collides with the living tissue.

When the piezoelectric device 110 is actuated for injection of liquid,driving noise uncomfortable for the ears of the operator of the liquidinjection device 10 is produced from the inside of the injectionmechanism 50. This driving noise is generated by the contraction andexpansion of the piezoelectric device 110, or vibration of componentssuch as the plate-shaped member 114 and the housing 112 for fixing thepiezoelectric device 110 caused by the reaction force produced when thepiezoelectric device 110 pressurizes the liquid within the liquidchamber 102.

Therefore, the liquid injection device 10 in this embodiment includes anoise reducing mechanism 118 for reducing driving noise (decreasingsound pressure of driving noise) generated by injection of liquid. Asillustrated in FIG. 2A, the noise reducing mechanism 118 includes amicrophone 120 (driving noise obtaining unit) which samples drivingnoise generated from the injection mechanism 50, a speaker 122 (pseudodriving noise outputting unit) which generates cancel sound (pseudodriving noise) for canceling (counterbalancing) the sampled drivingnoise, a cancel sound control unit 124 which controls the cancel soundgenerated based on the sampled driving noise, and others. According tothis embodiment, a space 116 is provided around the housing 112 and theplate-shaped member 114 within the case 100 of the injection mechanism50 as a space for accommodating the microphone 120 and the speaker 122.The speaker 122 is disposed in such a position as to face theplate-shaped member 114 as the chief source for generating the drivingnoise. According to this embodiment, the cancel sound control unit 124is provided separately from the case 100 of the injection mechanism 50.However, when the case 100 of the injection mechanism 50 has asufficient space, the cancel sound control unit 124 may be disposedwithin the case 100.

The case 100 of the injection mechanism 50 has through holes 126penetrated to connect the inside space 116 and the outside. According tothis embodiment, the six through holes 126 are formed on the end surfaceof the case 100 to which the speaker 122 is attached in such positionsas to surround the speaker 122 as illustrated in FIG. 3. When anabnormal operation condition such as mixture of bubbles into the liquidchamber 102 of the injection mechanism 50 occurs in the liquid injectiondevice 10 in this embodiment, cancel sound outputted from the speaker120 leaks through the through holes 126 to be heard, allowing theoperator of the liquid injection device 10 to easily recognizeoccurrence of the abnormal operation condition. This point will bedescribed in detail later. A mesh engages with each of the through holes126 to prevent entrance of contaminants into the case 100.

The liquid injection device 10 in this embodiment ejects liquid having ahigh flow speed from the injection port 132 as pulses, and also reducesdriving noise generated at the time of injection of liquid by using theinjection mechanism 50 thus constructed. The operation performed whenthe liquid injection device 10 in this embodiment outputs cancel soundused for reducing driving noise generated by injection of liquid is nowexplained.

B. Cancel Sound Output Operation in this Embodiment

FIG. 4 is a flowchart showing the flow of the process performed when theliquid injection device 10 in this embodiment outputs cancel sound(cancel sound control process). This process is executed by the cancelsound control unit 124 (corresponding to a pseudo driving noise dataproducing unit) in response to the start of liquid injection.

When the cancel sound control process is initiated, the microphone 120provided within the case 100 samples driving noise generated within thecase 100 of the injection mechanism 50 by injection of liquid (stepS100). As explained above, the liquid injection device 10 in thisembodiment applies driving voltage to the piezoelectric device 110 toeject liquid as pulses. Since the driving noise is produced by expansionof the piezoelectric device 110 caused when the driving voltage isapplied thereto, in step S100 the driving noise is sampled in suchcycles each of which continues from the time when the driving voltage isapplied until the time when the driving voltage is applied next.

After the driving noise is sampled, the phase of the sampled drivingnoise is reversed to produce cancel sound data having the opposite phase(sound data of pseudo driving noise) (step S102). Then, the producedcancel sound data is stored (step S104). The frequency of the drivingnoise is dependent on the frequency of the driving voltage applied tothe piezoelectric device 110 (driving frequency), and the frequencies ofthe intensive components of the driving noise are contained in thefrequency bands corresponding to the driving frequencies multiplied byintegers. This point will be described in detail later. According to theliquid injection device 10 in this embodiment, a cancel sound datamemory unit (pseudo driving noise data memory unit) is included in thecancel sound control unit 124, and the produced cancel sound data isstored in the cancel sound data memory unit.

After the cancel sound data having the phase opposite to the phase ofthe driving noise is stored, the cancel sound data is transmitted to thespeaker 122 at the time when the driving voltage is applied to thepiezoelectric device 110. Then, the cancel sound is outputted from thespeaker 122 based on the transmitted data (step S106). As explainedabove, the speaker 122 is disposed in such a position as to face theplate-shaped member 114 as the chief source for generating the drivingnoise (see FIG. 2A). Thus, emission of the driving noise uncomfortablefor the operator of the liquid injection device 10 can be reduced (thesound pressure of the driving noise can be decreased) by mutualcancellation between the driving noise and the cancel sound from thespeaker 122.

After the cancel sound is outputted from the speaker 122 based on thecancel sound data transmitted thereto, it is determined whetherinjection of liquid is stopped or not (step S108). While injection ofliquid is being stopped, that is, the piezoelectric device 110 is notbeing actuated, the driving noise is not produced. In this case, thecancel sound need not be outputted. Thus, whether injection of liquid isstopped or not is checked in the step S108.

While injection of liquid is being continued (step S108: NO), the flowreturns to the step S106 to reduce the driving noise generated byinjection of liquid. In this case, the cancel sound data is transmittedto the speaker 122 at the time when the driving voltage is applied tothe piezoelectric device 110, and the cancel sound is outputted from thespeaker 122. When injection of liquid is stopped after repetitions ofthe process of outputting the cancel sound from the speaker 122 everytime the driving voltage is applied to the piezoelectric device 110(step S108: YES), the cancel sound control process shown in FIG. 4 ends.

The liquid injection device 10 in this embodiment outputs the cancelsound having the phase opposite to the phase of the driving noise fromthe speaker 122 by executing the cancel sound control process explainedabove for reduction of the driving noise generated at the time ofinjection of liquid. As mentioned above, the liquid injection device 10in this embodiment stores the cancel sound data produced based on thedriving noise sampled by the microphone 120, and outputs the cancelsound by using the stored cancel sound data. Since the driving noise isreduced by the output of the fixed cancel sound, the cancel soundfunctions as alarm when an abnormal operation condition such as mixtureof bubbles into the liquid chamber 102 occurs. Thus, the operator of theliquid injection device 10 can easily recognize occurrence of theabnormal operation condition. This point is now explained in detail.

FIGS. 5A through 5D illustrate a condition in which the cancel soundfunctions as alarm when an abnormal operation condition such as mixtureof bubbles into the liquid chamber 102 of the injection mechanism 50occurs. FIG. 5A shows driving voltage applied to the piezoelectricdevice 110 for injection of liquid as an example condition. As explainedabove, when the driving voltage is applied to the piezoelectric device110, the piezoelectric device 110 expands and decreases the volume ofthe liquid chamber 102. As a result, the pressurized liquid within theliquid chamber 102 is injected from the injection port 132. When thedriving voltage applied to the piezoelectric device 110 is lowered afterthe liquid injection, the length of the piezoelectric device 110 returnsto the original length. Consequently, the volume of the liquid chamber102 returns to the original volume, allowing the liquid chamber 102 tobe filled with liquid. Then, the driving voltage is again applied to thepiezoelectric device 110 to eject high-pressure liquid from theinjection port 132. Accordingly, the driving voltage applied to thepiezoelectric device 110 in this manner achieves injection of liquid aspulses.

With injection of liquid as pulses, driving noise is generated withinthe case 100 of the injection mechanism 50. FIG. 5B shows a waveform ofthe driving noise generated by injection of liquid as an examplewaveform. This driving noise is chiefly produced by vibration of theplate-shaped member 114, the housing 112 and the like for fixing thepiezoelectric device 110 as vibration caused by the reaction forcegenerated when the liquid within the liquid chamber 102 is pressurizedby the press of the diaphragm 108 in accordance with the expansion ofthe piezoelectric device 110. Thus, the amplitude (sound pressure) ofthe driving noise has a tendency to increase in synchronization with thetime when the driving voltage is applied to the piezoelectric device110, and attenuate when the driving voltage is lowered. The frequency ofthe driving noise is dependent on the frequency of the driving voltageapplied to the piezoelectric device 110 (driving frequency), and thefrequencies of the intensive components of the driving noise arecontained in the frequency bands corresponding to the drivingfrequencies multiplied by integers. In case of the driving noise shownin FIG. 5B as an example, the components of the driving noise having thefrequency ten times higher than the driving frequency (3 kHz whendriving frequency is 300 Hz, for example) exhibit the maximum soundpressure, constituting the main components of the driving noise.

The liquid injection device 10 in this embodiment outputs cancel soundfrom the speaker 122 in response to the generated driving noise toreduce the driving noise. FIG. 5C shows a waveform of the cancel soundoutputted from the speaker 122 as an example. As explained above, thecancel sound data transmitted to the speaker 122 is produced byreversing the phase of the driving noise sampled by the microphone 120in such cycles each of which continues from the time when the drivingvoltage is applied to the piezoelectric device 110 until the time whenthe driving voltage is applied next. Thus, the frequency and amplitudeof the cancel sound are the same as those of the driving noise, and onlythe phase is reversed. The produced cancel sound data is stored, and thestored cancel sound data is transmitted to the speaker 122 every timethe driving voltage is applied to the piezoelectric device 110 foroutput of the cancel sound.

FIG. 5D illustrates the waveform of the driving noise shown in FIG. 5Band the waveform of the cancel sound shown in FIG. 5C as thesuperimposed waveforms. The operator of the liquid injection device 10hears sound having the waveforms thus superimposed. When the cancelsound is not outputted from the speaker 122, the driving noise isreleased as it is and heard by the operator. However, when the cancelsound having the phase opposite to the phase of the driving noise isoutputted from the speaker 122, the driving noise is reduced bycancellation between the driving noise and the cancel sound. As aresult, the operator hears little noise from the injection mechanism 50.When the driving voltage is applied to the piezoelectric device 110 infixed patterns with no bubble contained within the liquid chamber 102,the driving noise thus produced becomes substantially constant. Thus,the driving noise can be reduced (the sound pressure of the drivingnoise can be decreased) even by output of the cancel sound producedbased on the stored cancel sound data as in this embodiment.

When bubbles are mixed or generated within the liquid chamber 102, thedriving noise varies as shown in FIG. 5B. This phenomenon happens forthe following reason. Initially, as explained above, the driving noiseis chiefly produced by vibration of the plate-shaped member 114, thehousing 112 and the like by the effect of the reaction force generatedwhen the piezoelectric device 110 pressurizes the liquid within theliquid chamber 102. However, when bubbles are contained in the liquidchamber 102, these bubbles contract and absorb the pressure at the timeof pressurization of the liquid within the liquid chamber 102 by thepiezoelectric device 110. As a result, the reaction force decreases, andthe frequency and amplitude (sound pressure) of the driving noisechange. In case of the example shown in FIG. 5B, the sound pressure ofthe main components of the driving noise having the associated frequency(the frequency ten times higher than the driving frequency) when nobubble is contained in the liquid chamber 102 (during normal operation)considerably decreases. In this case, the liquid within the liquidchamber 102 is not sufficiently pressurized due to the presence of thebubbles, and the force of the liquid injected from the injection port132 lowers. As a result, the capability of incising or excising a livingtissue deteriorates. Accordingly, when bubbles are mixed or generatedwithin the liquid chamber 102, the operator of the liquid injectiondevice 10 is required to temporarily stop the operation to remove thebubbles by discharge from the injection port 132 or by other methods. Inaddition, the tendency that the driving noise generated by the actuationof the piezoelectric device 110 decreases is also recognized when theliquid within the liquid chamber 102 is not appropriately pressurized bythe piezoelectric device 110 due to breakage of the diaphragm 108 aswell as at the time when bubbles are contained in the liquid chamber102. In case of the breakage of the diaphragm 108, suspension of the useof the liquid injection device 10 is required.

The liquid injection device 10 in this embodiment outputs the cancelsound by using the stored cancel sound data without change even when thedriving noise varies by the mixture of the bubbles into the liquidchamber 102 or for other reasons. Therefore, as shown in FIG. 5C, thecancel sound outputted from the speaker 122 does not change before andafter the mixture of the bubbles. In this case, the frequencies andamplitudes of the driving noise varied by the mixture of the bubbles orthe like and the cancel sound outputted from the speaker 122 do notagree with each other, and therefore cancellation between the drivingnoise and the cancel sound becomes difficult.

According to the example shown in FIG. 5D, the cancel sound outputtedfrom the speaker 122 remains without cancellation due to the decrease inthe sound pressure of the driving noise caused by the mixture of thebubbles into the liquid chamber 102. As explained above, the case 100 ofthe injection mechanism 50 in this embodiment has the through holes 126(see FIG. 3). Thus, when the abnormal operation condition such asmixture of bubbles into the liquid chamber 102 occurs, the cancel soundnot cancelled leaks through the through holes 126 to be heard.Accordingly, since the cancel sound decreased by the cancellation withthe driving noise during the normal operation of the liquid injectiondevice 10 is heard by the operator of the liquid injection device 10 asnoise (alarm) at the time of occurrence of the abnormal operationcondition, the operator can easily recognize the operation abnormality.There is a case in which only the frequency of the driving noise variesdue to mixture of bubbles into the liquid chamber 102 or for otherreasons with the amplitude (sound pressure) of the driving noise keptunchanged unlike the example shown in FIG. 5B. In this case, the drivingnoise and the cancel sound do not have the opposite-phase relationshipbut are multiplied by each other. As a result, still larger abnormalnoise is heard.

As described above, the liquid injection device 10 in this embodimentstores cancel sound data having the phase opposite to the phase of thedriving noise generated by injection of liquid as data produced based onthe sampled driving noise, and outputs cancel sound from the speaker 122based on the stored cancel sound data every time the driving voltage isapplied to the piezoelectric device 110 for reduction of the drivingnoise. Thus, when the driving noise varies at the time of occurrence ofan abnormal operation condition such as mixture of bubbles into theliquid chamber 102 of the injection mechanism 50, the driving noisecannot be canceled by the cancel sound but is heard by the operator.Moreover, the cancel sound itself is heard by the operator. As a result,the operator of the liquid injection device 10 feels that noise (alarm)not heard by him or her before suddenly starts to be generated from theinjection mechanism 50, and therefore easily recognizes occurrence ofoperation abnormality.

The liquid injection device 10 in this embodiment samples actuallygenerated driving noise in each cycle continuing from the time when thedriving voltage is applied to the piezoelectric device 110 until thetime when the driving voltage is applied next by using the built-inmicrophone 120, and reverses the sampled driving noise to produce cancelsound data. In this case, the cancel sound outputted from the speaker122 obtains the same frequency and amplitude as those of the drivingnoise, and the opposite-phase relationship with the driving noise onlyby transmission of the cancel sound data to the speaker 122 at the timewhen the driving voltage is applied to the piezoelectric device 110 (insynchronization with the time when the driving voltage is applied).Thus, the driving noise during the normal operation can be appropriatelycancelled by the cancel sound and reduced with high accuracy.Accordingly, when an abnormal operation condition such as mixture ofbubbles into the liquid chamber 102 occurs, the operator easilyrecognizes the cancel sound heard as noise which functions as furthersecure notification about the operational abnormality.

When the operation is restored after discharge of the bubbles mixed inthe liquid chamber 102 from the injection port 132, the driving noiseand the cancel sound come to be cancelled by each other again in such acondition that emission of the driving noise can be sufficientlyprevented. Thus, the operator can easily recognize that the normalcondition of the liquid injection device 10 is restored.

C. Modified Example

A first modified example and a second modified example are hereinafterdescribed. In the explanation of the first modified example and thesecond modified example, similar reference numbers are given to partssimilar to the corresponding parts in the embodiment described above,and the same detailed explanation is not repeated.

C-1. First Modified Example

According to the embodiment described above, the cancel sound data isproduced based on driving noise sampled by the microphone 120 containedin the injection mechanism 50. However, considering the fact that thedriving noise generated by the actuation of the piezoelectric device 110during the normal operation is substantially constant for each patternof the driving voltage applied to the piezoelectric device 110, such astructure which stores the cancel sound data beforehand in accordancewith the patterns of the driving voltage applied to the piezoelectricdevice 110 is allowed. The first modified example explained hereinemploys this structure.

FIG. 6 illustrates the structure of the injection mechanism 50 mountedon the liquid injection device 10 according to the first modifiedexample. Unlike the embodiment described above (see FIGS. 2A and 2B),the liquid injection device 10 in the first modified example does nothave the microphone 120 for sampling driving noise. This is because theliquid injection device 10 in the first modified example stores cancelsound data beforehand in correspondence with the patterns of the drivingvoltage applied to the piezoelectric device 110 (driving voltagepatterns) such that the necessity of sampling the driving noise forproducing the cancel sound data as in the above embodiment can beeliminated.

According to the liquid injection device 10 in the first modifiedexample which sets a plurality of driving voltage patterns beforehand, adriving voltage pattern selection dial 202 may be connected with aninjection control unit 200 which controls the operation for applying thedriving voltage to the piezoelectric device 110. The operator of theliquid injection device 10 can select any of the plural driving voltagepatterns by switching the driving voltage pattern selection dial 202.The respective driving voltage patterns have different frequencies ofthe applied driving voltage (driving frequencies) and different levelsof the applied driving voltage such that the operator can vary theinjection cycle for injecting liquid from the injection port 132 aspulses and the level of the pressure of the liquid to be injected byswitching the driving voltage patterns.

When the operator of the liquid injection device 10 selects any of thedriving voltage patterns by using the driving voltage pattern selectiondial 202 and starts injection of liquid, the injection control unit 200applies the driving voltage to the piezoelectric device 110 incorrespondence with the driving voltage pattern selected by the drivingvoltage pattern selection dial 202 to actuate the piezoelectric device110. The injection control unit 200 is connected with the cancel soundcontrol unit 124 which controls cancel sound outputted from the speaker122 to notify the cancel sound control unit 124 of the selection of thedriving voltage pattern prior to the actuation of the piezoelectricdevice 110.

As explained above, the driving noise generated by the actuation of thepiezoelectric device 110 changes in accordance with the differentselections of the driving voltage pattern. Thus, as shown in FIG. 7, thecancel sound data memory unit contained in the cancel sound control unit124 stores individual cancel sound data in correspondence with therespective driving voltage patterns with correlations between the cancelsound data and the driving voltage patterns in advance. These cancelsound data are established as data for appropriately reducing drivingnoise generated when the driving voltage is applied to the piezoelectricdevice 110 in accordance with the corresponding driving voltage patternunder the condition in which no bubble is contained in the liquidchamber 102 (normal operation condition) (that is, data having the phaseopposite to the phase of the driving noise), and stored in such cycleseach of which continues from the time when the driving voltage isapplied until the time when the driving voltage is applied next.

The cancel sound control unit 124 reads the cancel sound datacorresponding to the driving voltage pattern selected by the drivingvoltage pattern selection dial 202 while referring to the table shown inFIG. 7, and transmits the cancel sound data to the speaker 122 at thetime when the driving voltage is applied to the piezoelectric device 110to output the cancel sound.

As illustrated in FIG. 6, in case of the liquid injection device 10 inthe first modified example, a frequency control dial 204 for controllingthe frequency of the cancel sound data, an amplitude control dial 206for controlling the amplitude of the cancel sound data, and a phasecontrol dial 208 for controlling the phase of the cancel sound data maybe connected with the cancel sound control unit 124. Moreover, finecontrol of the timing for transmitting the cancel sound data may beperformed by using a not-shown output timing control unit according tothe setting of the phase control dial 208. The driving noise generatedby the actuation of the piezoelectric device 110 slightly varies inaccordance with the different types of the liquid to be injected (thatis, liquid supplied to the liquid chamber 102) or the like in somecases. However, the operator of the liquid injection device 10 canestablish the condition for reducing the driving noise to the minimum byoperating these dials.

Accordingly, the liquid injection device 10 in the first modifiedexample can reduce the driving noise generated at the time of actuationof the piezoelectric device 110 by the cancellation between the drivingnoise and the cancel sound outputted from the speaker 122 under thenormal operation condition similarly to the embodiment described above.When the driving noise varies by occurrence of an abnormal operationcondition such as mixture of bubbles into the liquid chamber 102, thedriving noise cannot be cancelled by the cancel sound but is heard bythe operator of the liquid injection device 10. Moreover, the cancelsound itself is heard by the operator. Thus, the operator can easilyrecognize generation of the operational abnormality.

According to the liquid injection device 10 in the first modifiedexample, the cancel sound data is stored beforehand for each pattern ofthe plural established driving voltage patterns. Thus, the necessity ofproviding the microphone for sampling the driving noise inside theinjection mechanism 50 can be eliminated, which makes the injectionmechanism 50 compact. Moreover, the possibility of malfunction that thecancel sound data is produced based on sound obtained by the microphoneas sound existing therearound can be eliminated, which stabilizes thecondition for noise reduction.

Furthermore, when the frequency control dial 204, the amplitude controldial 206, and the phase control dial 208 are provided, the frequency,the amplitude, and the phase of the cancel sound can be controlled suchthat the driving noise actually generated can be reduced to the minimum.Thus, the driving noise during the normal operation can be reduced withhigh accuracy. Accordingly, when an abnormal operation condition such asmixture of bubbles into the liquid chamber 102 occurs, the operator ofthe liquid injection device 10 feels that the cancel sound heard asnoise has increased, and thus can easily recognize generation of theoperational abnormality.

C-2. Second Modified Example

According to the embodiment and the first modified example describedabove, the cancel sound is outputted based on the cancel sound datahaving the phase opposite to the phase of the driving noise. However,the cancel sound data is not limited to the data having the phaseopposite to the phase of the driving noise but may be sine wave cancelsound data for outputting the cancel sound. The second modified exampleexplained herein employs this structure.

FIGS. 8A through 8D show a condition in which the liquid injectiondevice 10 in the second modified example reduces driving noise by usingcancel sound outputted based on sine wave cancel sound data. FIG. 8Ashows driving voltage applied to the piezoelectric device 110 to ejectliquid as pulses. FIG. 8B shows a waveform of driving noise generated bythe actuation of the piezoelectric device 110 as an example.

For reducing this driving noise, the liquid injection device 10 in thesecond modified example transmits cancel sound data having a sinewaveform from the cancel sound control unit 124 to the speaker 122 tooutput the cancel sound. It is preferable that the sine waveform of thecancel sound data corresponds to the sine waveform at the frequencyexhibiting the largest sound pressure in the frequencies of the drivingnoise. In this case, the effect of noise reduction increases.

According to the liquid injection device 10 in the second modifiedexample, the frequency control dial 204, the amplitude control dial 206,and the phase control dial 208 (sine wave control unit) may be connectedwith the cancel sound control unit 124 similarly to the first modifiedexample (see FIG. 6). The operator of the liquid injection device 10 cancontrol the frequency, amplitude, and phase of the cancel sound data tobe transmitted to the speaker 122 by using these dials such that thedriving noise can be reduced to the minimum. The cancel sound controlunit 124 transmits the cancel sound data thus controlled to the speaker122 every time the driving voltage is applied to the piezoelectricdevice 110. FIG. 8C shows a waveform of cancel sound outputted from thespeaker 122 based on the cancel sound data controlled in accordance withthe driving noise as an example. For providing the opposite-phaserelationship between the driving noise generated by the actuation of thepiezoelectric device 110 and the cancel sound outputted from the speaker122, the cancel sound data having the same phase as that of the drivingnoise may be transmitted to the speaker 122 with delay of half cyclefrom the time when the driving voltage is applied to the piezoelectricdevice 110. Moreover, fine control of the timing for transmitting thecancel sound data may be performed by using the not-shown output timingcontrol unit in correspondence with the setting of the phase controldial 208.

FIG. 8D illustrates the waveform of the driving noise shown in FIG. 8Band the waveform of the cancel sound shown in FIG. 8C as superimposedwaveforms. Since the frequencies and amplitudes of the cancel soundoutputted from the speaker 122 and the driving noise actually generateddo not completely agree with each other, perfect cancellation cannot beachieved. However, the sound pressure of the noise heard by the operatorof the liquid injection device 10 can be reduced to be at least lowerthan when the cancel sound is not outputted at all.

When the driving noise varies at the time of occurrence of an abnormaloperation condition such as mixture of bubbles into the liquid chamber102 after the noise reduction, the cancel sound optimized for thedriving noise during the normal operation and the varied driving noiseare not cancelled by each other but multiplied by each other. As aresult, the operator feels that the noise has increased and thus caneasily recognize generation of operational abnormality.

As described above, the liquid injection device 10 in the secondmodified example may control the frequency, amplitude, and phase of thesine waveform cancel sound data such that the driving noise during thenormal operation can be reduced to the minimum for the output of thecancel sound. Considering the fact that the driving noise practicallygenerated when the driving voltage is applied to the piezoelectricdevice 110 contains various frequency components, output of the cancelsound capable of reducing the sound pressure of the driving noisegenerated during the normal operation can be easily achieved bycontrolling the frequency, amplitude, phase of the cancel sound data inaccordance with the actual driving noise based on the sine waveformcancel sound data.

According to the example shown in FIG. 8C, the amplitude of the cancelsound approximated by sine waves becomes constant after the control bythe amplitude control dial 206. However, since the amplitude of thedriving noise practically generated tends to attenuate with decrease inthe driving voltage, the amplitude of the cancel sound may be madeattenuate accordingly. In this case, when an attenuation factor controldial for controlling the attenuation factor of the amplitude of thecancel sound data is connected with the cancel sound control unit 124,the waveform of the cancel sound can be made similar to the waveform ofthe driving noise, which further improves the accuracy of noisereduction.

The liquid injection device according to the invention is not limited tothe embodiment and respective modified examples described herein but maybe practiced otherwise without departing from the scope of theinvention.

1. A liquid injection device injecting liquid from an injection nozzle,comprising: a liquid chamber which receives supply of the liquid andconnects with the injection nozzle; a liquid chamber volume varying unitto which driving voltage is applied to reduce the volume of the liquidchamber to a volume smaller than the volume of the liquid chamber beforethe driving voltage is applied; a driving voltage applying unit whichapplies the driving voltage to the liquid chamber volume varying unitwith the liquid supplied to the liquid chamber; a pseudo driving noisedata memory unit which stores sound data of pseudo driving noise havingat least a part of audible frequency components contained in drivingnoise generated when the driving voltage is applied to the liquidchamber volume varying unit; and a pseudo driving noise outputting unitwhich outputs the pseudo driving noise by using the sound data of thepseudo driving noise such that the sound pressure of the driving noisedecreases within the audible frequency range when the driving voltage isapplied.
 2. The liquid injection device according to claim 1, whereinthe pseudo driving noise data memory unit is a unit which stores thesound data of the pseudo driving noise in accordance with the drivingvoltage applied to the liquid chamber volume varying unit.
 3. The liquidinjection device according to claim 1, wherein the pseudo driving noiseoutputting unit is a unit which decreases the sound pressure of thedriving noise within the audible frequency range by outputting thepseudo driving noise with delay from the time when the driving voltageis applied.
 4. The liquid injection device according to claim 3, whereinthe pseudo driving noise outputting unit has an output timing controlunit which controls the time when the pseudo driving noise is outputtedwith delay from the time when the driving voltage is applied.
 5. Theliquid injection device according to claim 1, wherein: the pseudodriving noise data memory unit stores sound data of the pseudo drivingnoise having the phase opposite to the phase of at least apart of theaudible frequency components of the driving noise; and the pseudodriving noise outputting unit is a unit which decreases the soundpressure of the driving noise in the audible frequency range byoutputting the pseudo driving noise in accordance with the time when thedriving voltage is applied.
 6. The liquid injection device according toclaim 1, further comprising: a driving noise obtaining unit whichobtains the driving noise generated when the driving voltage is applied;and a pseudo driving noise data producing unit which produces sound dataof the pseudo driving noise based on the obtained driving noise, andthen allows the pseudo driving noise data memory unit to store the sounddata.
 7. The liquid injection device according to claim 1, wherein thepseudo driving noise data memory unit is a unit which stores sound datahaving the sine waveform corresponding to any one frequency of audiblefrequency components contained in the driving noise as sound data of thepseudo driving noise.
 8. The liquid injection device according to claim7, wherein the pseudo driving noise outputting unit has a sine wavecontrol unit which controls at least either the phase of the sinewaveform or the amplitude of the sine waveform to output the pseudodriving noise by using sound data of the pseudo driving noise obtainedafter control of at least either the phase or the amplitude of the sinewaveform.